[1] The Eunicid anatomy typically consists of a pair of appendages near the mouth (mandibles) and complex sets of muscular structures on the head (maxillae) in an eversible pharynx.

[12] In 2020, Zanol et al. stated, "Species traditionally considered to belong to Eunice are now, also, distributed in two other genera Leodice and Nicidion recently resurrected to reconcile Eunicidae taxonomy with its phylogenetic hypothesis.

[4] Throughout the 1800s (1832-1878) worm species were added to this genera by Jean Victor Audouin and Henri Milne-Edwards, Kinberg, Edwardsia de Quatrefages, Malmgren, Ehlers and Grube.

[4] In 1944, Hartman codified a system of separate classification for the family, informally grouping North American species using the original suggestions of Ehlers.

Eunicidae jaws are typically well developed and partly visible on the underside of the worm or on its surface at the front of the mouth in a complex structure.

For example, the Eunice aphroditois crawl on the seafloor where they scavenge in a carnivorous feeding pattern on marine worms, small crustaceans, molluscs, algae and detritus.

[2][14][22][23][24] Other species, for example Euniphysa tubifex and large Eunice, hunt the surrounds of their coral habitats and feed on the decaying flesh of dead sea-life.

[2][25] The practice of harvesting polychaetes (including species in the Eunicidae family) as bait may have negative ecological impacts on intertidal habitats and on worm population numbers.

[9] The ecological impacts of bait harvesting activity can also affect associated fauna populations [10] as well as sediment quality [28] and bioavailability of heavy metals.

[31][32] Alien species can threaten the foundation of local ecosystems by altering food webs, habitat structures and gene pools.

[31] Live bait worms are often emptied into the water body by anglers at the end of a fishing session, this is another practice that can introduce alien species to aquatic ecosystems.

[6] In the Florida Keys for example, the swarming of Eunice fucata is a highly publicised in local fishing communities, attracting a large gathering of tarpon.

[6] These mass swarming events, or ‘risings’, are a spectacle that is the foundation of local tradition in Samoa, Fiji, Tonga, Papua New Guinea, Vanuatu, Kiribati and Indonesia.

[8] For example, in the Venice lagoon, fisherman dig below the sediment layers colonised by the nereidids and sieve organic material through coarse screens.

[7] Eunice aphroditois, another sizeable (up to 1 metre in length) species of Eunicidae, is harvested by scuba divers along the Italian Apulia coasts.

[7] This species is collected at soft bottom ocean floors at a depth of 10 metres using specialised harvesting instruments that fit into U-shaped parchment tubes where the worm lives.

[7] Species within the Eunicidae family are also caught by recreational and commercial fisherman in estuaries along the West coast of Portugal and in Arcahon Bay in France.